Bug#646900: [multipath-tools] Errors when Boot On SAN (IBM DS4700)

[Frido Roose]

Hello,

When adding a script "add_rdac_handler" with the contents below - which
loads scsi_dh_rdac as soon as possible - to
the /etc/initramfs-tools/scripts/init-top/ directory, the number of io
errors after loading initrd has diminished (only a coupple of "read failed"
messages but no more end_request I/O errors
And more importantly, the boot delay has improved alot.

The message log looks more sane, like:

Jan  4 11:58:50 raiti kernel: Write protecting the kernel read-only data:
10240k
Jan  4 11:58:50 raiti kernel: Freeing unused kernel memory: 1060k freed
Jan  4 11:58:50 raiti kernel: Freeing unused kernel memory: 1788k freed
Jan  4 11:58:50 raiti kernel: rdac: device handler registered
Jan  4 11:58:50 raiti kernel: usb 1-1: new high speed USB device using
ehci_hcd and address 2
Jan  4 11:58:50 raiti kernel: device-mapper: multipath: version 1.2.0 loaded
Jan  4 11:58:50 raiti kernel: device-mapper: multipath round-robin: version
1.0.0 loaded
Jan  4 11:58:50 raiti kernel: udev[281]: starting version 164
<snip>
Jan  4 11:58:50 raiti kernel: scsi 0:0:0:0: Direct-Access     IBM      1815
     FAStT  0914 PQ: 0 ANSI: 5
Jan  4 11:58:50 raiti kernel: scsi 0:0:0:0: rdac: LUN 0 (unowned)
Jan  4 11:58:50 raiti kernel: sd 0:0:0:0: [sda] 2097152 512-byte logical
blocks: (1.07 GB/1.00 GiB)
Jan  4 11:58:50 raiti kernel: scsi 0:0:0:1: Direct-Access     IBM      1815
     FAStT  0914 PQ: 0 ANSI: 5
Jan  4 11:58:50 raiti kernel: sd 0:0:0:0: [sda] Write Protect is off
Jan  4 11:58:50 raiti kernel: scsi 0:0:0:1: rdac: LUN 1 (unowned)
Jan  4 11:58:50 raiti kernel: sd 0:0:0:0: [sda] Write cache: enabled, read
cache: enabled, supports DPO and FUA
Jan  4 11:58:50 raiti kernel: sd 0:0:0:1: [sdb] 584888320 512-byte logical
blocks: (299 GB/278 GiB)
Jan  4 11:58:50 raiti kernel: sd 0:0:0:1: [sdb] Write Protect is off
Jan  4 11:58:50 raiti kernel: sd 0:0:0:1: [sdb] Write cache: enabled, read
cache: enabled, supports DPO and FUA
Jan  4 11:58:50 raiti kernel: sda:Dev sda: unable to read RDB block 0
Jan  4 11:58:50 raiti kernel: unable to read partition table
Jan  4 11:58:50 raiti kernel: scsi 0:0:1:0: Direct-Access     IBM      1815
     FAStT  0914 PQ: 0 ANSI: 5
Jan  4 11:58:50 raiti kernel: scsi 0:0:1:0: rdac: LUN 0 (owned)
Jan  4 11:58:50 raiti kernel: sdb:Dev sdb: unable to read RDB block 0
Jan  4 11:58:50 raiti kernel: unable to read partition table
Jan  4 11:58:50 raiti kernel: sd 0:0:0:0: [sda] Attached SCSI disk
Jan  4 11:58:50 raiti kernel: sd 0:0:0:1: [sdb] Attached SCSI disk
Jan  4 11:58:50 raiti kernel: scsi 0:0:1:1: Direct-Access     IBM      1815
     FAStT  0914 PQ: 0 ANSI: 5
Jan  4 11:58:50 raiti kernel: sd 0:0:1:0: [sdc] 2097152 512-byte logical
blocks: (1.07 GB/1.00 GiB)
Jan  4 11:58:50 raiti kernel: scsi 0:0:1:1: rdac: LUN 1 (owned)
Jan  4 11:58:50 raiti kernel: sd 0:0:1:1: [sdd] 584888320 512-byte logical
blocks: (299 GB/278 GiB)
Jan  4 11:58:50 raiti kernel: sd 0:0:1:0: [sdc] Write Protect is off
Jan  4 11:58:50 raiti kernel: sd 0:0:1:0: [sdc] Write cache: enabled, read
cache: enabled, supports DPO and FUA
Jan  4 11:58:50 raiti kernel: sd 0:0:1:1: [sdd] Write Protect is off
Jan  4 11:58:50 raiti kernel: sd 0:0:1:1: [sdd] Write cache: enabled, read
cache: enabled, supports DPO and FUA
Jan  4 11:58:50 raiti kernel: sdc: unknown partition table
Jan  4 11:58:50 raiti kernel: sdd: unknown partition table
Jan  4 11:58:50 raiti kernel: sd 0:0:1:0: [sdc] Attached SCSI disk
Jan  4 11:58:50 raiti kernel: sd 0:0:1:1: [sdd] Attached SCSI disk
Jan  4 11:58:50 raiti kernel: scsi 1:0:0:0: Direct-Access     IBM      1815
     FAStT  0914 PQ: 0 ANSI: 5
Jan  4 11:58:50 raiti kernel: scsi 1:0:0:0: rdac: LUN 0 (unowned)
Jan  4 11:58:50 raiti kernel: sd 1:0:0:0: [sde] 2097152 512-byte logical
blocks: (1.07 GB/1.00 GiB)
Jan  4 11:58:50 raiti kernel: scsi 1:0:0:1: Direct-Access     IBM      1815
     FAStT  0914 PQ: 0 ANSI: 5
Jan  4 11:58:50 raiti kernel: sd 1:0:0:0: [sde] Write Protect is off
Jan  4 11:58:50 raiti kernel: scsi 1:0:0:1: rdac: LUN 1 (unowned)
Jan  4 11:58:50 raiti kernel: sd 1:0:0:0: [sde] Write cache: enabled, read
cache: enabled, supports DPO and FUA
Jan  4 11:58:50 raiti kernel: sd 1:0:0:1: [sdf] 584888320 512-byte logical
blocks: (299 GB/278 GiB)
Jan  4 11:58:50 raiti kernel: sd 1:0:0:1: [sdf] Write Protect is off
Jan  4 11:58:50 raiti kernel: sde:Dev sde: unable to read RDB block 0
Jan  4 11:58:50 raiti kernel: sd 1:0:0:1: [sdf] Write cache: enabled, read
cache: enabled, supports DPO and FUA
Jan  4 11:58:50 raiti kernel: unable to read partition table
Jan  4 11:58:50 raiti kernel: scsi 1:0:1:0: Direct-Access     IBM      1815
     FAStT  0914 PQ: 0 ANSI: 5
Jan  4 11:58:50 raiti kernel: sdf:
Jan  4 11:58:50 raiti kernel: sd 1:0:0:0: [sde] Attached SCSI disk
Jan  4 11:58:50 raiti kernel: scsi 1:0:1:0: rdac: LUN 0 (owned)
Jan  4 11:58:50 raiti kernel: Dev sdf: unable to read RDB block 0
Jan  4 11:58:50 raiti kernel: unable to read partition table
Jan  4 11:58:50 raiti kernel: sd 1:0:0:1: [sdf] Attached SCSI disk
<snip>

The device section of multipath.conf in initrd looks like:
device {
        vendor                  "IBM"
        product                 "1815"
        path_grouping_policy    group_by_prio
        path_checker            rdac
        checker                 rdac
        hardware_handler        "1 rdac"
        prio                    rdac
        failback                immediate
        no_path_retry           queue
    }

root at server:# cat /etc/initramfs-tools/scripts/init-top/add_rdac_handler
#!/bin/sh

PREREQ=""
prereqs()
{
echo "$PREREQ"
}
case $1 in
# get pre-requisites
prereqs)
prereqs
exit 0
;;
esac

modprobe scsi_dh_rdac
modprobe dm_multipath
modprobe dm_round_robin
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